Measurement of the Strong Interaction Shift and Width of the Ground State of Pionic Hydrogen

Hyperfine Interactions - An experiment to measure the strong interaction width (Γ1s ) and shift (ε1s ) of the ground state of pionic hydrogen (π?p), in order to determine the...     

Ultrafast predissociation dynamics of water molecules excited to the electronic C and D states

Two-photon excitation with femtosecond laser pulses in the spectral range 240-250 nm was used to prepare vapor phase H(2)O and D(2)O in the C (1)B(1) and D (1)A(1) states. Both states are predissociated via the B (1)A(1) state, forming excited OH/OD(A (2)Sigma(+)) as well as ground state OH/OD(X (2)Pi). We used ultrashort infrared probe pulses (1.65-2.42 microm) to control the ratio between these excited and ground state fragments originating from the dissociation process. Time resolved detection of the OH/OD(A (2)Sigma(+)) --> OH/OD(X (2)Pi) fluorescence allows us to monitor the dynamics of the predissociation. For the heterogeneous predissociation out of the C(1)B(1) state life times of (0.5 +/- 0.1) ps and (1.2 +/- 0.1) ps were found for H(2)O and D(2)O, respectively. The purely homogeneous character of the predissociation out of the D (1)A(1) state was monitored.     

High pressure treatment of pharmaceutical drug delivery and related systems

Abstract

Solids like layer silicates (kaolinite and montmorillonite) as well as ZnO are in use in pharmacy. They are pressure treated and subsequently analyzed by means of ESR spectroscopy. The structural changes indicated by Fe³⁺ ions and paramagnetic defects are reponsible for the enhanced chemical activity of the pressurized systems.

Especially active Fe-O-species are formed which can react with intercacalated organic molecules. The most probable first step of such reactions will be a solid state single electron transfer. Spin probes and spin traps were used to prove this statements. The activation of the drug delivery systems by mechanical treatments is of importance for the stability of the drugs incorporated.     

First direct observation of coulomb explosion during the formation of exotic atoms

A Doppler broadening of x-ray transitions from pionic nitrogen and muonic oxygen, which is attributed to Coulomb explosion of the molecules, has been observed by using a crystal spectrometer. Large linewidths indicate fast ionization of the molecules and a charge of (3-4)e for the accelerated fragments.     

Determination of Spin Concentrations in ESR Tomography as Applied for the Spatial Distribution of Spin Labels in Human Skin

The spectral–spatial electron spin resonance (ESR) imaging experiment provides information about the spatial and spectral properties of the examined sample, as well as the intensity distribution. Obtaining quantitative statements of the respective sample requires the usage of reference standards such as diphenylpicrylhydrazyl (DPPH) or charcoal. By means of ultraviolet-visible spectroscopy a DPPH sample has been quantified to become the reference DPPH standard for the following experiments. Moreover, charcoal together with DPPH serves as a standard to determine the spatial dimension. An ESR tomographic device has been modified concerning the sample shaping and arranging in a TE₁₀₂ resonator to allow the spatially resolved quantitative determination of spin concentrations of spin probes (S = 1/2) with an acceptable error. Only standard ESR equipment has been used except the additional gradient coils and their computer-aided controls for recording the tomogram. The presented results, i.e., the spatially resolved determination of spin concentrations, seem to be useful to describe, e.g., transport processes in biological objects. As a first application of the developed method, the spatial resolution of the effect of ultraviolet irradiation on the concentration of a spin probe in human skin could be determined. Altogether, the newly introduced method widens the field of applications of ESR spectroscopy and tomography. Authors' address: Werner Herrmann, Institute of Pharmacy, Free University Berlin, Kelchstrasse 31, 12169 Berlin, Germany